The bacterial communities of Alaskan mosses and their contributions to N2-fixation

Hannah Holland-Moritz,Stuart F Mcdaniel,Samantha N Miller,Michelle C Mack,Julia E M Stuart,Lily R Lewis,Jose Miguel Ponciano,Noah Fierer

doi:10.1186/s40168-021-01001-4

Abstract

BackgroundMosses in high-latitude ecosystems harbor diverse bacterial taxa, including N2-fixers which are key contributors to nitrogen dynamics in these systems. Yet the relative importance of moss host species, and environmental factors, in structuring these microbial communities and their N2-fixing potential remains unclear. We studied 26 boreal and tundra moss species across 24 sites in Alaska, USA, from 61 to 69° N. We used cultivation-independent approaches to characterize the variation in moss-associated bacterial communities as a function of host species identity and site characteristics. We also measured N2-fixation rates via 15N2 isotopic enrichment and identified potential N2-fixing bacteria using available literature and genomic information.ResultsHost species identity and host evolutionary history were both highly predictive of moss microbiome composition, highlighting strong phylogenetic coherence in these microbial communities. Although less important, light availability and temperature also influenced composition of the moss microbiome. Finally, we identified putative N2-fixing bacteria specific to some moss hosts, including potential N2-fixing bacteria outside well-studied cyanobacterial clades.ConclusionsThe strong effect of host identity on moss-associated bacterial communities demonstrates mosses’ utility for understanding plant-microbe interactions in non-leguminous systems. Our work also highlights the likely importance of novel bacterial taxa to N2-fixation in high-latitude ecosystems.D9s3_gqDR2-mjeknv8S5sZVideo

Highlights

Mosses are ubiquitous in northern ecosystems, often forming the dominant ground cover in boreal forests, peatlands, and Arctic tundra [1]
These results indicate that there is a strong signal of both host identity and host phylogeny on moss bacterial community composition and this signal is independent of differences in site-level environmental conditions
Regardless, our results suggest that host species identity, rather than measured or unmeasured environmental factors, is a more consistent indicator of bacterial community structure and that moss species distributions may be more relevant than site characteristics for understanding the contributions of the moss microbiome to ecosystem processes, including N2fixation

Summary

Introduction

Mosses are ubiquitous in northern ecosystems, often forming the dominant ground cover in boreal forests, peatlands, and Arctic tundra [1]. Moss-associated microbes fix N2 [3, 4, 7], oxidize methane [8, 9], and contribute to the decomposition of organic matter in moss-dominated tundra and peatlands [10]. For these reasons, there has long been an interest in understanding what microbes (2021) 9:53 associate with mosses, their contributions to ecosystem processes, and the factors that structure moss-associated microbial communities (e.g., [11,12,13,14]). We measured N2-fixation rates via 15N2 isotopic enrichment and identified potential N2-fixing bacteria using available literature and genomic information

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Results

Discussion

Conclusion